Sasha Kondratyeva said she was on a treadmill Monday evening when she heard a loud bang followed by screams. She ran over to see what was happening and started recording from above with her iPhone.

The five-second video shows the 30-year-old suspect walking away from the scene of the shooting in which 45-year-old Maria Lucas from Olivette was killed.

The victim worked in the reception area as a supervisor.

The suspect, who was identified only as a part-time janitor at the facility, was later shot and seriously wounded during a shootout with police.

In the video, what appears to be a gun can be seen in his left hand. He walks by two people in the lobby, who appear to be unaware of the danger.

“I saw the guy walking with the gun,” Kondratyeva said. “I saw the people in the reception area. They were ducking and underneath their desks.”

Kondratyeva described how, at first, it was unclear what was happening.

“What was interesting is the guy seemed like he had an employee shirt on, and as I was talking to a staff member next to me, I was like, ‘Do you know him? Does he work here?’ And he’s like, ‘Yeah, I know him!’” she said.

“About a minute after that, we heard five or six shots, just pow-pow-pow-pow-pow-pow and that’s when everybody just started screaming and just running and seeing where we could see available to hide.”

She wrote on Facebook: “They are shooting at the Maryland Heights Community Center right now. Currently hiding in the closet in one of the fitness rooms. Please pray for us.”

Kondratyeva said, “I was like okay, I guess this is my last Facebook post I’m going to make.”

About 30 minutes later, she said, police escorted her past the crime scene, where she took a photo of a blood trail in the lobby and videos of police escorting them to safety.

“I keep replaying it in my head, just the same thing over and over,” Kondratyeva said.

Maryland Heights Police Chief Bill Carson said there were no other injuries in the shooting.

The suspect had worked for the city of Maryland Heights for less than three years.